<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    * {
      margin: 0;
      padding: 0
    }

    .waterfall {
      height: 100vh;
      display: grid;
      grid-template-rows: repeat(48, 1fr);
      grid-gap: 2px;
      grid-auto-flow: row dense;
      /* grid-auto-rows: 20px; */
    }

    .waterfall .item {
      background: pink;
      /* color: #ddd; */
    }

    .waterfall .item:nth-of-type(1) {
      grid-row: 1 / 12;
      grid-column: 1 / 3;
    }

    .waterfall .item:nth-of-type(2) {
      grid-row: 1 / 19;
      grid-column: 3 / 4;
    }

    .waterfall .item:nth-of-type(3) {
      grid-row: 12 / 49;
      grid-column: 1 / 2;
    }

    .waterfall .item:nth-of-type(4) {
      grid-row: 15 / 19;
      grid-column: 2 / 3;
    }

    .waterfall .item:nth-of-type(5) {
      grid-row: 19 / 32;
      grid-column: 2 / 3;
    }

    .waterfall .item:nth-of-type(6) {
      grid-row: 19 / 32;
      grid-column: 3 / 4;
    }
  </style>
</head>

<body>
  <div class="waterfall">
    <div class="item">1</div>
    <div class="item">2</div>
    <div class="item">3</div>
    <div class="item">4</div>
    <div class="item">5</div>
    <div class="item">6</div>
  </div>
</body>

</html>